return set of all equivalence uris
return set of all equivalence uris

nbargnesi/openbel-server,nbargnesi/openbel-server,OpenBEL/openbel-server,OpenBEL/openbel-server,OpenBEL/openbel-api,OpenBEL/openbel-server,OpenBEL/openbel-api,OpenBEL/openbel-api,nbargnesi/openbel-server,OpenBEL/openbel-api